Abstract/Summary

The largest landslides on the south coast of England are those associated with failure surfaces in
montmorillonite-rich mudstones close to the base of the Gault Formation (mid Cretaceous).
Those at Folkestone, Sussex (Trenter & Warren, 1996), Ventnor, Isle of Wight (Hutchinson,
2001) and Black Ven, west Dorset (Brunsden, 2002) are among the largest active landslide
systems in the UK. Westwards from Dorset, the Gault facies of the Albian Stage is replaced on
the east Devon coast by sandstones and sandy calcarenites of the Upper Greensand Formation.
These are mostly moderately strong rocks that crop out in almost continuous, precipitous cliffs
between Sidmouth and the county boundary at Lyme Regis. They are a major component of the
landslide debris, but the formation itself has not previously been shown to have initiated a
failure. For example, the extensive Bindon landslide [SY 277 895] near Axmouth, which
incorporates large masses of Upper Greensand, was attributed to failure surfaces in the Gault
(Conybeare et al., 1840). However, that formation has not been recorded in a coastal section west
of Lyme Regis.